Liquid clarification apparatus



Jan. 12, 1960 cju ETAL 2,920,763

LIQUID CLARIFICATION APPARATUS Filed March 6, 1956 2 Sheets-Sheet 1 '56 O g 0 D Z I Z INVENTORSj firth/a1 C. Lind 0 William Jlfatz,

Awoigh'y A. c. LIND EI'AL LIQUID CLARIFICATION APPARATUS Jan. 12, 1960' 2 Sheets-Sheet -2 Filed March e, 1956 INVENTORS .flrthar 6'. Lind William, JKatz,

ATTO EY United States Patent O F .LIQUID CLARIFICATION APPARATUS Application March 6, 1956, Serial No. 569,715

1 Claim. (Cl. 210-221) This invention relates to the clarification of liquids which are carrying suspended impurities, such as sewage, industrial wastes and the like, and has for its principal object the provision of an improved apparatus for continuously separating theimpurities from the carrying liquid with a high degree of efficiency, whereby the liquid may be discharged from the apparatus in a substan tially pure state while the impurities may be either sent to waste or recovered for further use if desired.

The impurities carried by the liquids with which the invention is primarily concerned usually have a specific gravity approximately the same or only slightly higher than that of the carrying liquid, and although at least a substantial portion of them usually can be separated from the liquid by sedimentation, such procedure is so rela tively slow that where great quantities of liquid must be handled, large and expensive installations are necessary. On the other'hand, it has been previously recognized thatin view of the near-equality of the specific gravities of the liquid and the impurities, separation of the two may also be accomplished by flotation methods having at least some analogy to those widely employed in the separation of ores, i.e, by subjecting the impure liquid to the action of air or other gas bubbles which attach themselves to the suspended impurities and float them to the liquid surface.

It is also known that in the clarification of liquids in this manner the best results are obtained through the use of gas bubbles of extremely small size and several methods and means for providing minute bubbles have been proposed, among them the entrainment or dissolution of the gas in water, which mixture is then introducedinto a body of-the impure liquid contained in a clarification tank of appropriate size. One of the principal difliculties encountered in a system of this character has been incomplete mixing of the impure liquid with the gas-liquid solution resultingin low hydraulic efliciency and consequent large size in the clarification.

apparatus. Accordingly, it is a principal object of the present invention to provide at least two hydraulic zones, in the first of which control may be exercised over the the second of which flotation of suspended particles may take place. It is a corollary object to the foregoing to provide a proper mechanical and hydrostatic combina-.

tion of the zones whereby the mixed incoming flow is caused to disperse throughout the flotation zone and utilize the full volume thereof, with consequent improved ple in the accompanying drawings constituting a part of this specification, in which:

Figure l is a plan view of a typical form of the apparatus, with the skimming mechanism for removing the" mixing of impure liquid with gas-liquid solution and in 2,920,763 Patented Jan. 12,1960:

floated impurities from the liquid surface omitted for the. sake of clearness;

Fig. 2 is a side elevational view of the apparatus shown in Fig. 1, with the skimming mechanism in place;

Fig. 3 is a central longitudinal sectional view of the' apparatus shown in Figs. 1 and 2, looking in a direction opposite to that of Fig. 2;

Fig. 4 is a transverse sectional view taken on the plane indicated by the line 4-4 in Fig. 3, looking in the direction of the arrows;

Fig. 5 is a view similar to'Fig. 4 but taken on the, plane indicated by the line 55 in Fig. 3, looking in the direction of the arrows;

Fig. 6 is a fragmentary longitudinal sectional view. similar to Fig. 3 of a slightly modified form of the apparatus; and v Fig. 7 is a fragmentary transverse sectional view on the planes indicated by the line 77 in Fig. 6, looking; in the direction of the arrows.

Referring more particularly to Figs. 1-5 inclusive, 10 indicates an open-topped clarification tank, here shown as constructed of metal and comprising the side walls: 11 and 12, end walls 13 and 14, and a bottom wall or floor 15. A pipe or conduit 16 conducts the impure liquid to the said tank, into which it is introduced through the branches 17 extending through the end wall 13 and discharging behind a baffle 18. A pipe 19 extends through the opposite end wall 14 for discharging the clarified liquid from the tank.

At the head or influent end of the tank there is provided a transverse partition 20 extending from the floor 15 to somewhat above the liquid level 21 and dividing the tank into a comparatively small influent or mixing chamber 22 and a considerably larger separation or flotation chamber 23. As best shown in Fig. 4 the partition; wall 20 is provided with a transverse series of relatively narrow vertical slots or perforations 24 extending substantially from top to bottom of the wall and aflord-ing. restricted communication between the chambers 22 and 231 throughout substantially their entire cross sectional area.

,The partition 20 is preferably retained by guide ways (not shown) fixed to the side walls 11 and 12 so that the partition may be removed for periodic cleaning.

At the discharge or effluent end of the tank it is provided with a second transverse partition 25, the upper portion of which is equipped with a vertically adjustable weir 26 whereby the liquid level in the chamber 23 may; be controlled. Since, as will be clear from Figs. 2 and q 3, the effluent pipe 19 is located at the upper portion of the tank; the space between the partition 25 and the end wall 14 constitutes a well 27 in which a quantity .transverse bafile plate 30 depends from the scum trough- 28 as shown in Figs. 3 and 5, and in conjunction with said trough prevents floated impurities from reaching the weir 26 thereby insuring that only clarified liquid} will exit from the chamber 23 to the well 27.

As best shownin Figs. 1 and 2, the apparatus for supplying gasusually air--to the impure liquid comprises a motor-driven pump 31 mounted-exteriorlvof the tank 10 and from the intake side of whicha suction pipe 32 extends into the wet-well 27 I The discharge side .ofsaid pump is connected by alpipe 33 to the lower po "tion of a closed tank 34'and said pipe 33 is providedwi'th" .a -connection;35-"through-which air or other gas may be supplied to the liquid flowing through such pipe for dis solution therein. The tank ,34 has a vertical bafile 36 extending across it and upwardly from its bottom to adjacent i-ts top, and the pipe 33 dischargesinto -said tank to one side of such bafile while a pipe"37 leads'from the tank-at the other side-of the baffle. Thetank 34 is of such capacity in relation to the flow-of liquidprovided by the pump 31' that the liquid will be held in'said tank under pressure fora-time sufficientusually from one to two minutesfor it .to'become substantially saturated with the gas introduced through the connection "35. The baffle 36 insures detention of the liquid for the necessary period by preventing short-circuiting thereof between the pipes-33 and 37.

The pipe 37 leads to -an automatic pressure-regulating valve 38 located adjacent the exterior of the influent c'hamber22, and a pipe 39 leads fromsuch valve to a dist'ribution-header-40 whichjis disposed in and'extends across the lower portion of said influent chamber, adjacent the end wall 13 of the tank 10. Thesaid header may comprise a length of pipe providedwith a longitudinal series of perforations41through which the pressurized gas-saturated liquid from the pipe 39 may be discharged into the raw impure liquid in said chamber H m the form of upwardly and rearwardly directed jets. Inasmuch as the liquid in the chamber 22 is under only normal atmospheric pressure, the discharge of the superatmospherically pressurized gas-saturated liquid thereinto has the elfect of liberating the gas in the form of myriads of minute bubbles which, in the case of many impure liquids, are thoroughly dispersed through the body of such liquid in said chamber bythe agitating action of the jets alone. In the case of some impure liquids however, it may be desirable to assist this dispersal by means of mechanical agitators such as the rotatable paddles 42 located in the receiving chamber.

The liquid in chamber 22- is continuously transferred therefrom to the chamber 23 through the perforated partition 20, which protects the liquid in the latter chamber against substantially all of the agitation taking place in the former chamber and provides a relatively quiescent body of liquid in which the minute gas bubbles may the better attach themselves to the suspended impurities-and carry them to the surface of the liquid. The combined area of the series of slots 24 in the partition 20 is much less than the cross sectional area of the tank and the said partition thus creates a hydraulic head in the chamber 22 which is sufficient to produce substantially complete diffusion of the liquid and gas bubbles passing through the slots 24 to all parts of the chamber 23, thereby avoiding short-circuiting and leaving no dead spots in the body of liquid in such chamber. As a"result the efficiency of the present apparatus is appreciably'higher than that of the previously proposed installations of similar nature and for any given volume of impure liquid to be handled, it may be correspondingly smaller.

A valve-controlled pipe 43, communicating with the chamber 23 adjacent the .effluent end of tank 10, may be provided for draining the tank when necessary.

As" shown in Figs. 2-5,,mechanical skimming mechanism may be provided for positively removing the floated impurities from the tank. This mechanismcomprises a framework 45 surmounting the tank ,10 and including superposed pairs of .transversely spaced guides or rails 46 y and 47 which. respectively support the upper and lowerruns of a pair of endless chains 48 that are trained about head sprockets .49 and tail sprockets 50 which are suitably, journaled insaid framework. The head sprockets49, are driven by'an appropriate source of power 5.1 through a chain-and-sprocket drive 52. The chains 48 pendently' carry between them a plurality. of transversely extending skimming ,blades"53 which, during their travel from left. to right .as viewed in Fig; 3,',break the surface 21 of the liquid in both of the chambers 22 and 23 of the tank 10 and positively move any material floating on said surface to and into the receptacle 28, from which it is discharged through the pipe 29. An inclined apron 54 may be provided ahead of the upper portion of the partition 20 to assist the blades 53 in transfer of the floatage in chamber 22 over said partition.

In the form of the apparatus illustrated in Figs. 6 and 7 the mechanical agitator is omitted from the chamber 22 of the tank, and the difiusion partition 55, instead of being slotted as in Fig. 4, is provided with a plurality of holes 56 through which the liquid and gas bubbles pass from the chamber 22 to the chamber 23. A combined sludge and skimming conveyor 57, of a flight type well known in sewage treatment and other liquid purification fields, is shown in lieu of the skimming mechanism above described and illustrated in Figs. 2-5. Such impurityremoving mechanism may be desirable in certain cases wheresome of the impurities will unavoidably settle-to the floor 15 of the tank even though most of themcan be floated to the liquid surface.

In some applications the rates of flow and characteristics-of the liquid being treated may indicate the desirability of a non-mechanical mixer, one type of which is illustrated in Fig. 6. As shown, the form of mixer comprises abaffle 18 which extends transversely from the side wallsof the tank and upwardly above the liquid level in the tank 10. At its lower edge the baffle 18 terminates slightly above the distribution header 40. A horizontal ba'flle 58 is shown fixed to the wall 13 at an elevation above the header 40, it being understood that this baffle likewise extends transversely between the sidewalls of the tank. The forward edge of the horizontal bafile 58, in conjunction with the lower edge of the vertical baffle 18' creates -a slit-like opening 59 through which all of the influent liquid must pass. The perforations 41 in header 40 may be oriented to direct jets of pressurized gas-saturated liquid across this opening 59 so that thorough mixing of the two streams occurs.

Fig. 6 also illustrates a revolving scum pipe 60 of a type well 'known in the art for removing scum in the mixing zone 22, it being understood that such a device may not be required in all instances. The details of scum pipe 60 are completely described in Patent No. 2,337,859 to F. G. Stuller. It is operated by tilting its open top until one edge of the opening is slightly submerged, in which position water will flow into the pipe carrying floating scum therewith.

What is claimed is:

Apparatus for the continuous separation of impurities from liquids in which they are suspended, comprising an open tank, for containing a body of the liquid under normal atmospheric pressure; a perforated partition in said tank dividing it into-a single localized influent chamber and a single substantially larger separation chamber, the apertures in said partition providing restricted communication between-such chambers whereby a hydraulic head may be maintained in the influent chamber, and said apertures being sospatially arranged in the partition as to insurediffusion of fluid passing therethrough to all portions of the separation chamber while at the same time preventing undue agitation of the body of liquid in such chamber, thus maintaining it in a relativelyquiescent state most conducive to flotation of the impurities carried thereby; means for supplying the impure liquid to said influent chamber; means for continuously discharging directly. into the impure liquid in said influent chamber a super-atmospherically. pressurized liquid containing a dissolved gas which gas is liberated in the form of minute bubbles by the pressure drop within the chamber, which bubbles upon passage through theperforated partition under the action -of said hydraulic head are -diifused toall parts -ofsaid separation chamber, said discharging means comprising a perforatedheader extending transversely ofv the localized influent, chamber in the lower portion thereof; baflie means in the influent chamber arranged to direct the entire impure liquid influent to the region of said pressurized-liquid discharging means, said bafiie means comprising a vertical baffle element arranged to direct the incoming impure liquid downwardly to the region of said header, and a horizontal bafiie element adjacent the lower portion of said vertical element, the lower edge of the vertical element and the rearward edge of the horizontal element being spaced to provide between them a narrow horizontally extending discharge port adjacent the header through which said impure liquid influent is discharged across the pressurized-liquid discharge whereby to efiect a thorough blending of the two liquids; means for discharging clarified liquid from the separation chamber; and means for removing the separated impurities from the chambers.

References Cited in the file of this patent UNITED STATES PATENTS 1,583,141 Greenawalt May 4, 1926 6 Forrester Oct. 18, 1927 McTaggart Ian. 28, 1930 Ruth Feb. 11, 1930 Forrester June 6, 1933 Weinig Jan. 10, 1939 McKenna Oct. 31, 1939 MacIntosh Aug. 12, 1941 Henkel Nov. 23, 1943 Janis Apr. 27, 1954 Kelly et a1. July 12, 1955 Baum May 22, 1956 Juell Oct. 9, 1956 Brown et a1. Oct. 9, 1956 Banks et a1 Nov. 12, 1957 FOREIGN PATENTS Great Britain July 3, 1922 Italy Mar. 18, 1938 

